More than $100,000 from oil and real estate interests has been funneled into city council races in Sonoma County’s two largest cities, highlighting how outside groups have ponied up to influence voters in the Nov. 6 election.

Of the pair of independent expenditure campaigns, the most visible has been in Petaluma, where a committee backed by several large oil companies has poured more than $78,000 into the race for mayor, according to campaign finance records.

The second spending effort is by a national real estate group that has spent more than $31,000 in favor of several city council candidates in Petaluma and Santa Rosa.

In Petaluma especially, the rush of outside spending has caused a stir. The two campaigns there have separately generated mailers supporting two mayoral candidates — Mike Harris and Brian Powell — and online ads and mailers supporting Harris and two others running for council seats, incumbent Dave King and candidate Michael Regan.

Brian Sobel, a Petaluma- based political analyst and former city councilman, called the level of outside spending in the city election unprecedented.